Let A=(123012001)A = \begin{pmatrix} 1 & 2 & 3 \\ 0 & 1 & 2 \\ 0 & 0 & 1 \end{pmatrix}A=100210321. Apply the rank-nullity theorem to find dim(Null(A))\dim(\text{Null}(A))dim(Null(A)) (the nullspace dimension).
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